Here's why:

* Solids: Particles in solids are tightly packed together in a fixed, rigid structure. They have very little space to move around, resulting in the closest spacing.

* Liquids: Particles in liquids are closer together than in gases, but they can move around and slide past each other.

* Gases: Particles in gases are very far apart and move freely in all directions.

Think of it this way: Imagine a crowd of people. In a solid, everyone is crammed together, shoulder to shoulder. In a liquid, they can move around a bit but are still relatively close. In a gas, everyone is spread out and can move freely.